in pictures | Successful launch of the James Webb Space Telescope

The James Webb Space Telescope (JWST), which astronomers around the world have waited for 30 years to examine the universe in unparalleled means, blasted off an Ariane 5 rocket on Saturday to reach its observation center, 1.5 million kilometers from Earth.

We’ll know 27 minutes after take-off if the propulsive phase of the flight went well.

With liftoff from the Guyana Space Center, which happened on time at 12:20 a.m. (GMT), JWST will become the most advanced universe-monitoring instrument ever sent into space. But it will take another month to reach its final location.

With the aim of enlightening humanity more in two questions that torment them: “Where did we come from?” and “Are we alone in the universe?”

Thus we see the glimmer of the “cosmic dawn”, when the first galaxies began to illuminate the universe after the Big Bang, 13.8 billion years ago.

It will make it possible to better understand the formation of stars and galaxies, to observe exoplanets from which astronomers are discovering more and more samples, in order, perhaps, to learn about other planets on Earth one day.

James Webb will follow in the footsteps of the Hubble telescope, which revolutionized the observation of the universe: thanks to it, scientists discovered the presence of a galactic black hole in the center of all galaxies, or the presence of water vapor around exoplanets.

Envisioned by NASA since the launch of Hubble in 1990, and built from 2004 in collaboration with the European Space Agencies (ESA) and Canada (CSA), JWST stands out in many ways.

The size of its mirror, with a wingspan of 6.5 meters, gives a surface area and therefore a sensitivity seven times greater, which is enough to detect the thermal signature of a bumblebee on the moon.

Another difference: the method of observation. Where Hubble observes space primarily in the visible light field, James Webb ventures into the wavelength that eludes the eye: the near and mid-infrared. Radiation that objects, stars, people, or flowers emit naturally.

This light will be studied by four instruments, equipped with imaging devices and spectrophotometers to better dissect it. Their development mobilized a large number of engineers and scientists, under the leadership of American and European laboratories and industrialists.

Thanks to this, “Looking at the same things [qu’avec Hubble]We’ll see new things, explained astronomer Pierre Ferrouette, the telescope’s co-scientific director at the European Space Agency, in Paris. For example, the first galaxies, objects whose lights turned red after their distance. Or the colonies of young stars that grow hidden in the clouds of dust in their nurseries. or the atmosphere of the outer planets.

A prerequisite for the correct operation of the JWST is an ambient temperature that is too low to interfere with the light inspection.

Hubble orbits at an altitude of 600 km above Earth. At this distance, JWST would be unusable, heated by the Sun and its reflection on Earth and the Moon.

It will be placed at the end of a one-month journey 1.5 million kilometers away. It will be shielded from solar radiation by a heat shield of five flexible heat-dissipating sails, lowering the temperature (80 degrees) to -233 degrees Celsius on the side of the telescope.

But before getting there, the machine and its designers will have to achieve a real breakthrough: its flawless deployment, with a series of operations that includes, for example, for the shield alone 140 opening mechanisms, 400 reels and nearly 400 meters of cable.

Because the observatory, 12 meters high and a shield equivalent to a tennis court, had to be folded to slip into the Ariane 5 cover. The “wrapping” was carried out with laser guidance to avoid any damage to the device, a development that cost about ten billion dollars was developed.

For these maneuvers, NASA has also imposed drastic hygiene measures to prevent any contamination of the telescope mirror by particles or even charged breathing…

Finally, a specially designed aerodynamic decompression system was installed by Arianespace so that, when separated from the actuator, at an altitude of 120 km, a sudden change in pressure would not damage the beast. “Exceptional customer, exceptional measures,” an ESA official explained Thursday in Kourou.

It will take several weeks to see if the telescope is ready for use. With formal entry into service scheduled for June.